The invention relates to a flexible sandwich panel, comprised of a center layer and at least one outer layer, where the center layer is made of a polymeric synthetic material, is itself flexible and exhibits a coarse-cell honeycomb structure with open cells in the direction of the upper and lower side of the center layer, and at least one outer layer or two outer layers that is/are laminated to at least one side of the center layer and that covers or cover said center layer.
Honeycomb structures made of aluminum and fiber papers have been known since the nineteen fifties as core material with a high compressive strength. In the nineteen eighties, honeycomb structures made of thermoplastic synthetics were developed. In particular, polypropylene and polycarbonate have been used as synthetic materials. In the meantime, certain companies in the industry (such as WACOTECH GmbH and Co. KG; TUBUS WABEN GmbH and Co. KG, of Rxc3x6ttenbach, Germany) are offering light, cost-efficient honeycomb structures in a density range of 12 kg/m3 to 80 kg/m3 with various hole diameters.
A flexible sandwich panel of the type mentioned above is referred to in the German Patent Publication DE 298 09 543 U1. This document describes a sandwich panel with a coarse-cell honeycomb support core that is provided with a fiber-enforced top layer. The top layer encases the fiber core. Thermoplastic layers and foils are named as the top layers.
A sandwich panel with such thermoplastic top layers is ill suited for use as a building panel, because, in particular, ceramic panels, such as tiles or other ceramic elements and also strips and boards made of wood materials, cannot be attached easily using simple adhesive technology. Furthermore, the top layers made of synthetic materials are not flame resistant.
It is, therefore, the principal objective of the present invention to specify a sandwich panel that does not exhibit the aforementioned disadvantages but instead, similar to known mortar-coated panels, offers on its exterior side a surface suitable for attaching ceramic panels or panels made of wood materials, and that is largely flame resistant, yet exhibits a high degree of flexibility.
This objective, as well as other objectives which will become apparent from the discussion that follows, are achieved, in a flexible sandwich panel of the type mentioned above, wherein the outer layer, or at least one of the two outer layers, comprises hardened mortar that is made flexible with synthetic additives, and that has as its core a web material consisting of fibers, and wherein the exterior side of the hardened outer layer is lept unrefined or roughcast in a plaster-like manner.
A mortar suitable for the exterior layers is set forth in various compositions in the description that follows.
As generally known with sandwich panels, the core web material can be connected, in particular welded or glued, to the top side of the center layer. The web material may consist of polymeric fibers in the form of a non-woven material, a woven fabric or a knit fabric, or may consist of glass fibers in the form of a non-woven material, a woven fabric or a knit fabric. Cellulose fibers in the form of a non-woven material may be used as web material as well. With woven or knit fabrics, the average stitch diameter is preferably at most 50% of the mean diameter of a honeycomb of the honeycomb structure of the center layer.
To retain the advantage of light weight and of good thermal insulation, the mortar belonging to an outer layer should fill a maximum of 33% of the hollow space volume of the center layer. On its outer side, the external layer at a certain fill ratio exhibits numerous flat holes that coincide with the openings of the cells and that provide an increased adhesion surface.
For the sandwich panel, cement preferably serves as the mineral component of the mortar on the external layer, but gypsum may also be used. The compressive strength of the sandwich panel, which can be set through the parameters of the center and outer layers, should be set to at least 10 N/cm2 on the outer side that is covered with an outer layer.
The thickness of the un-laminated center layer is preferably between 5 and 25 mm; it consists preferably of polyolefin or polyolefin copolymers; if desired, also of polyester, polycarbonate or polyamide.
The sandwich panel is particularly well suited for use as a building panel and carrier for additional layers, such as wallpaper, paint applications, facing tiles and soundproofing panel elements. Another important type of use is that as an interim layer element between a pipe laying panel covered with pipes, in particular for floor heating, and a top layer that can be walked on, for example parquet boards or carpet floors.
For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings.